Putter shaft extension

ABSTRACT

This invention is a putter shaft extension assembly which is especially suitable for use in converting a putter with a conventional shaft length into a longer shaft “belly putter”. It uses a novel screw attachment and pin arrangement to prevent accidental loosening and improper assembly. It is also preferably supplied with spacers to provide different extension lengths, these spacers also contain pins to prevent accidental loosening of the extension.

This invention is an extension for a putter shaft which uses spacers to provide different extension lengths and a system of pins to prevent unwanted loosening. The pins, spacers, and threaded attachment method are designed to make incorrect assembly virtually impossible. The extension is especially suitable for extending a conventional putter shaft so the putter can be used as a mid-length “belly” putter.

BACKGROUND

1. Description of Prior Art

Putting can be a frustrating part of a golfer's game and consequently golfers often try putters with different shaft lengths to improve this part of their game. Conventional length putters typically have overall lengths of 84 cm (33 inches) to 91 cm (36 inches) and are held only in the golfer's two hands. A putter with a longer overall length, typically 104 cm (41 inches) to 114 cm (45 inches), is commonly called a mid-length, or belly putter. The belly putter has a longer shaft than a conventional putter which enables the golfer to place the end of the shaft into his navel, thereby helping to stabilize the putter. Putters with even longer shafts are sometimes used in which the shaft end is placed in the golfer's sternum or even his chin, and these putters are commonly called long putters.

If a golfer has a conventional length putter but would like to try a longer putter, a belly putter for instance, this can be difficult and expensive. Belly putters are not commonly found in golf pro shops and smaller golf retailers, and therefore it is not easy to “demo” one to see if it is a fit for the golfer. Usually the golfer must purchase a belly putter, from an on-line retailer for instance, and they are typically more expensive than conventional putters. Also, there is no good way, apart from trying several putters, to determine a shaft length that is most suitable. If the golfer randomly chooses a length and orders that length, he may face purchasing one or more additional putters to obtain a suitable shaft length. In many cases, this expense and difficulty prevents golfers from trying belly putters. A putter shaft extension which could easily and inexpensively convert an existing putter into a belly putter or long putter and which could provide different extension lengths, would aid golfers in their effort to try these longer putters.

A consideration in any putter shaft extension, especially one that is adjustable, is acceptance by the United States Golf Association (USGA) as conforming to the rules of golf. One applicable USGA rule is that all adjustable parts must be firmly fixed and that there is no reasonable likelihood of them coming loose during play. Friction fit methods of adjustment are generally not permitted because they are not considered firmly fixed. Another important rule is that the adjustment cannot be readily made but must require the use of a special tool such as a screwdriver or Allen key. Another consideration which appears to be desirable to the USGA is that an assembly which can be installed or removed from a golf club has design features which make it virtually impossible for the user to install incorrectly. Several prior art patents appear to fall short of one or more of these rules.

2. Objects and Advantages

It is an object of this invention to provide an extension for a putter shaft which uses spacers to provide different extension lengths and pins to prevent accidental loosening.

It is a further object of this invention to provide an extension for a putter shaft which is virtually impossible to assemble incorrectly, helping insure its conformance with the rules of golf.

Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.

BRIEF DESCRIPTION OF DRAWING FIGURES

FIG. 1, shows a cross-sectional view of a preferred embodiment of a putter shaft extension of this invention taken through the axis of the extension.

FIGS. 2 and 3 show preferred embodiments of putter shaft extensions of this invention which use a spacer to provide longer extension lengths than that shown in FIG. 1, these figures also being cross-sectional views through their axes.

FIGS. 4, 5, and 6 show in exploded perspective some critical parts of the extensions shown in FIGS. 1, 2, and 3.

FIG. 7 is similar to FIG. 6 except it shows a pinning means which is a tab integrally machined into a member, and

FIG. 8 shows an end view of a milled cavity suitable for use with this pinning tab.

FIG. 9 shows the assembly of FIG. 2 attached to a putter shaft which is attached to a putter head, this drawing also being a cross-sectional view taken through the common axis of the putter shaft and the extension assembly.

REFERENCE NUMERALS IN DRAWINGS

-   1 short length putter shaft extension assembly -   2 intermediate length putter shaft extension assembly -   3 long length putter shaft extension assembly -   8 golf club head -   10 putter shaft -   12 putter grip -   14 putter grip hole -   16 putter shaft insert -   16′ putter shaft insert with clearance cavity for machined tab -   18 threaded hole -   20 clearance hole for dowel pin -   21 clearance cavity for tab -   22 dowel pin -   23 tab -   24 press fit hole for dowel pin -   26 extension handle -   26′ extension handle with integrally machined tab -   27 extension handle clearance screw hole -   28 extension handle grip -   30 extension handle grip hole -   41 short spacer -   42 short spacer clearance screw hole -   43 long spacer -   43′ long spacer with integrally machined tab and clearance cavity     for tab -   44 long spacer clearance screw hole -   51 short length screw -   52 intermediate length screw -   53 long length screw

DESCRIPTION AND OPERATION—FIGS. 1 TO 7

FIG. 1 shows a short length putter shaft extension assembly 1 of this invention installed on a golf putter shaft 10 with a putter grip 12. Assembly 1 includes a putter shaft insert 16 with a threaded hole 18 at its axis; insert 16 is secured in putter shaft 10 through a hole 14 in putter grip 12. Assembly 1 also includes a dowel pin 22 which freely engages an off-axis clearance hole 20 in insert 16. Also included in assembly 1 is an extension handle 26 containing an off-axis press fit hole 24 in which dowel pin 22 is secured. Extension handle 26 has a clearance hole 27 at its axis for free passage of a short length screw 51 for engagement in threaded hole 18 in insert 16. A grip 28 is installed on extension handle 26 in which a hole 30 has been provided to install screw 51 and access it with a screwdriver (not shown).

FIG. 2 shows an intermediate length shaft extension assembly 2 of this invention which is similar to short length assembly 1 except this extension also includes a short spacer 41 with an axial clearance hole 42 for free passage of an intermediate length screw 52. This assembly uses two dowel pins 22, a first dowel pin which is the same dowel pin 22 shown in FIG. 1 except in this case it freely engages a clearance hole 20 in short spacer 41. A second dowel pin 22 is secured in a press fit hole 24 in short spacer 41 and this second dowel pin 22 engages clearance hole 20 in insert 16. Intermediate assembly 2 provides a longer shaft extension than assembly 1, this additional length being the length of short spacer 41.

FIG. 3 shows a long length extension assembly 3 which is similar to intermediate length extension assembly 2 except an even longer extension is provided by using a long spacer 43 and a long length screw 53. Long spacer 43 has an axial clearance hole 44 for long length screw 53 and is provided with an off-axis press fit hole 24 holding a dowel pin 22 which engages pin clearance hole 20 in insert 16. Spacer 43 has an off-axis clearance hole 20 which freely accepts the dowel pin 22 pressed into extension handle 26.

FIGS. 4, 5, and 6 show exploded perspective views of the critical portions of assemblies 1, 2, and 3.

FIG. 7 shows a modification of the extension shown in FIG. 6 wherein dowel pins 22 have been replaced by two tabs 23 which are machined into an extension handle 26′ and a spacer 43′. The tabs 23 engage two clearance cavities milled into insert 16 (becoming insert 16′) and spacer 43 (now spacer 43′) shown by way of example in FIG. 8 as clearance cavity 21. Cavity 21 is similar in shape to tabs 23 and of sufficient depth to allow complete insertion of tabs 23 into spacer 43′ and insert 16′.

FIG. 9 shows the intermediate length extension assembly 2 installed in putter shaft 10 which is attached to a putter head 8.

The procedure for installing and using extension assembly 1 with a putter is as follows. First, hole 14 must be provided in putter grip 12. This can be done either with grip 12 installed on putter shaft 10, or it may be provided before grip 12 is installed on shaft 10. Then insert 16 is secured in shaft 10, preferably using a suitable adhesive such as epoxy, but other mechanical methods are possible such as a press fit. The product is preferably supplied to the user with dowel pin 22 already pressed and secured in hole 24 in extension handle 26. The projecting end of dowel pin 22 is inserted in clearance hole 20 of insert 16 and short screw 51 is started in threaded hole 18 and tightened, securing extension handle 26 to insert 16 and thus to putter shaft 10. If a longer extension is desired, such as that provided by assembly 2 or 3, screw 51 is removed, short spacer 41 or long spacer 42 is inserted between extension handle 26 and insert 16, dowel pins 22 are inserted into their respective clearance holes 20, and intermediate screw 52 is used to secure if short spacer 41 is used or long screw 53 is used if long spacer 43 is used.

Conformance with the rules of golf and acceptance by the USGA is an important consideration in this invention. As discussed above, it is desirable, therefore, to have a putter extension which not only can be assembled and used to conform to the rules of golf, but additionally has features which make it virtually impossible to assemble and use in a manner which is not conforming. Two aspects of this invention provide this explicit conformance while covering two important USGA rules.

As discussed in the prior art section, one rule is that any club with adjustable parts must have its parts firmly fixed with no reasonable likelihood of them working loose during a round of golf. Inventor has found that extension handle 26 with grip 28 can act like a “screwdriver handle” to inadvertently loosen screw 51, 52, or 53. Pin(s) 22, positioned off-axis, working with screws 51, 52, or 53, positioned axially, severely limit rotation of extension handle 26 relative to insert 16, thereby preventing this undesirable loosening of screw 51, 52, or 53.

Another rule is that when extension shaft assembly 1, 2, or 3 is installed, it must be straight with putter shaft 10; the axis of shaft 10 must be essentially collinear with the axis of assembly 1, 2, or 3. If any pin 22 of assemblies 1, 2, or 3 is not properly placed in its clearance hole 20, it would be a “bump” which would cause a misalignment when assembly 1, 2, or 3 was installed on shaft 10. Two features are incorporated in this invention to prevent assembly unless all pins of assemblies 1, 2, and 3 are properly engaged in their clearance holes 20, thereby preventing misalignment.

The first feature is the fact that hole 18 in insert 16 is shown as being only partially threaded; it is not completely threaded through insert 16 but has a limited full thread length. Screws 51, 52, and 53 used for this product typically come completely threaded, and therefore if hole 18 were totally threaded, long length screw 53 could tighten not only assembly 3, but also assemblies 1 and 2. But since hole 18 is only partially threaded, long screw 53 can only enter hole 18 a limited distance which is approximately the full thread length of hole 18. It can readily be seen that by choosing a full thread length for hole 18 which is only slightly longer than the thread engagement distance of screws 51, 52, and 53 when tightened in hole 18 in assemblies 1, 2, and 3 respectively, it is impossible to use the wrong screw in any of these assemblies. For instance, with the above limitations, if an attempt was made to use intermediate length screw 52 in short assembly 1, screw 52 would bottom in hole 18 before any tension existed in screw 52. Extension handle 26 would be noticeably loose and wobbly, rendering extension assembly 1 useless. Conversely, if an attempt was made to use short screw 51 in intermediate assembly 2, screw 51 would not be long enough to engage the threads in hole 18 and extension handle 26 could not be secured to insert 16. Therefore, by limiting the full thread length of hole 18, by partial threading for instance, it is possible to design assemblies 1, 2, and 3 so that the proper screw 51, 52, and 53 must be used with each assembly 1, 2, and 3 respectively. If short spacer 41 has a length of 2.5 mm (1 inch) and long spacer 43 has a length of 5 mm (2 inches), then intermediate screw 52 should be 2.5 mm (1 inch) longer than short length screw 51 and long length screw 53 should be 2.5 mm (1 inch) longer than intermediate length screw 52. If hole 18 has a full thread length of about 9 mm (0.35 inches) and screws 51, 52, and 53 in assemblies 1, 2 and 3 respectively have thread engagement distances of about 6 mm (0.25 inches), then the proper screw 51, 52, or 53 must be used in each assembly 1, 2, and 3.

Since the proper screw 51, 52, or 53 must be used in each assembly 1, 2, and 3, to insure that all pins used in assemblies 1, 2, and 3 engage their clearance holes 20 it is only necessary to make the insertion distance of all pins 22 into their respective clearance holes 20 greater than the thread engagement length of screws 51, 52, and 53 when tightened in hole 18. Then, if any pin 22 is not properly engaged in its clearance hole 20, screws 51, 52, and 53 cannot engage the threads of hole 18 and extension handle 26 cannot be fastened to insert 16. This therefore insures that an incorrectly positioned pin 22 cannot cause a misalignment of extension assembly 1, 2, or 3 with shaft 10.

Inventor believes a preferred way to transfer torque between adjacent members of these extension assemblies is by using dowel pin(s) 22 having one end secured in a press fit hole 24 in one member and having its other end inserted in a clearance hole 20 of its adjacent member. But FIG. 7 shows how a tab 23 integrally machined into a member inserted into an appropriately shaped and sized clearance cavity in the adjacent member, such as clearance cavity 21 shown in FIG. 8, can also provide this torque transfer. The semicircular shape shown for tab 23 is but one of many possible shapes which would work. The important point is that all adjacent extension parts, insert, extension handle, and spacer, have a projection with one end fixed to a part and with its other end entering and engaging an appropriate cavity in the adjacent part. This will “pin” the parts together thereby severely restricting relative rotation between all adjacent parts of the extension. This ultimately prevents rotation between the extension handle and the insert, thereby preventing unintentional loosening of the extension's attachment screw.

SUMMARY, RAMIFICATION, AND SCOPE

In summary, this invention is an extension for a putter shaft which, in its shortest version, is an extension handle attached to an insert secured in the grip end of a putter shaft. In a preferred embodiment, the extension uses an axial screw tightened in a partially threaded hole in the insert to force the extension handle against the insert. An off-axis pin, working cooperatively with the screw, prevents accidental loosening of the screw. Different extension lengths are obtained using appropriately longer screws and spacers placed between the extension handle and insert. Off-axis pins are also used with the spacers to prevent accidental loosening of these longer screws even with the spacers installed. The partially threaded hole in the insert requires the use of the proper screw for each length assembly. This, combined with sufficient pin projections from the members in which they are secured, makes assembly impossible unless all pins are properly engaged in their clearance holes. Therefore, the extension and putter shaft must be assembled correctly and the extension is straight with the putter shaft.

Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments. For instance, the attachment screw is shown as being axial with the pins off-axis, but they could reverse positions, or both could be off-axis. An example is shown of a pinning projection which is a semicircular tab integrally machined into a member for engagement into an appropriately shaped clearance hole of its adjacent member, but other shapes are possible. Dowel pins are discussed as being preferably pressed into an appropriately under-sized hole, but a threaded stud secured in a threaded hole would also work. Two spacers could be stacked together to obtain an even longer overall extension length, and by using appropriate pins in both spacers, accidental loosing of the extension could still be prevented. Other modifications could be made which do not affect the essence of the invention. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given. 

1. An apparatus which extends a putter shaft, the apparatus comprising: a first member secured in the putter shaft; a threaded hole in the first member; a second member; a hole in the second member; a threaded fastener having a portion which passes through the hole in the second member and engages threads in the threaded hole in the first member; a thread engagement distance of the threaded fastener with the threaded hole in the first member wherein a tension exists in the threaded fastener which forces the second member to contact the first member; a pinning projection having a first end which is secured to one of the two members and a second end which entered a cavity in the other member a distance greater than the thread engagement distance when the second member was forced to contact the first member; whereby the threaded fastener and pinning projection cooperatively limit rotation of the second member relative to the first member and whereby the threaded fastener can engage the threads of the threaded hole in the first member only when the second end of the pinning means has entered its cavity.
 2. The apparatus of claim 1 wherein the first end of the pinning projection is secured to the second member.
 3. The apparatus of claim 1 wherein the first end of the pinning projection is secured to the first member.
 4. The apparatus of claim 1 wherein an axis of the putter shaft is collinear with an axis of the first member and an axis of the second member.
 5. The apparatus of claim 1 wherein an axis of the threaded hole in the first member is parallel with an axis of the putter shaft.
 6. The apparatus of claim 1 wherein an axis of the threaded hole in the first member is collinear with an axis of the putter shaft.
 7. The apparatus of claim 1 wherein the first member is secured in the putter shaft with an adhesive.
 8. The apparatus of claim 1 wherein the threaded hole in the first member has a maximum thread engagement distance for any suitably threaded fastener.
 9. The apparatus of claim 8 wherein the threaded hole in the first member is only partially threaded.
 10. The apparatus of claim 1 wherein the pinning projection is a dowel pin whose first end is secured in a hole in either member and whose second end entered a clearance hole in the other member a distance greater than the thread engagement distance.
 11. The apparatus of claim 1 wherein the pinning projection is a tab with its first end an integral part of the second member.
 12. The apparatus of claim 1 wherein the pinning projection is a tab with its first end an integral part of the first member.
 13. An apparatus which extends a putter shaft, the apparatus comprising: a first member secured in the putter shaft; a threaded hole in the first member; a second member; a hole in the second member; a spacer located between the first member and the second member; a hole in the spacer; a relatively long threaded fastener having a portion which passes through the hole in the second member and the hole in the spacer and engages threads in the threaded hole in the first member; a thread engagement distance of the threaded fastener with the threaded hole in the first member wherein a tension exists in the threaded fastener which forces the second member to contact the spacer and the spacer to contact the first member; a first pinning projection having a first end which is secured to the spacer and a second end which entered a cavity in one of the two members; a second pinning projection having a first end which is secured to the other of the two members and a second end which entered a cavity in the spacer; whereby the threaded fastener, the spacer, the first pinning projection, and the second pinning projection cooperatively limit rotation of the second member relative to the first member.
 14. The apparatus of claim 13 wherein the second end of the first pinning projection and the second end of the second pinning projection entered their respective cavities a distance greater than the thread engagement distance when the second member was forced to contact the spacer and the spacer was forced to contact the first member, whereby the threaded fastener can engage the threads of the threaded hole in the first member only when the second ends of both pinning projections have entered their respective cavities.
 15. The apparatus of claim 13 wherein the first pinning projection is a dowel pin with its first end secured in a hole in the spacer and the cavity its second end entered is a clearance hole in the first member, and the second pinning projection is a dowel pin with its first end secured in a hole in the second member and the cavity its second end entered is a clearance hole in the spacer.
 16. The apparatus of claim 13 wherein the first pinning projection is a dowel pin with its first end secured in a hole in the spacer and the cavity its second end entered is a clearance hole in the second member, and the second pinning projection is a dowel pin with its first end secured in a hole in the first member and the cavity its second end entered is a clearance hole in the spacer.
 17. The apparatus of claim 13 wherein the first pinning projection is a tab with its first end an integral part of the spacer.
 18. The apparatus of claim 13 wherein the second pinning projection is a tab with its first end an integral part of the second member.
 19. The apparatus of claim 13 wherein the second pinning projection is a tab with its first end an integral part of the first member.
 20. An apparatus which extends a putter shaft, the apparatus comprising: a first member secured to the putter shaft; a second member; a spacer placed between the first member and the second member; a threaded fastener having a portion which passes through a hole in the second member and a hole in the spacer and engages threads in a threaded hole in the first member; a thread engagement distance of the threaded fastener with the threaded hole in the first member wherein a tension exists in the threaded fastener which forces the second member to contact the spacer and the spacer to contact the first member; a first pin secured to and projecting from the second member in which the first pin enters a hole in the spacer when the threaded fastener forces the second member to contact the spacer; a second pin secured to and projecting from the spacer in which the second pin enters a hole in the first member; whereby the threaded fastener, spacer, and pins cooperatively limit rotation of the second member relative to the first member. 